1. Field of the Invention
The present invention relates to an image forming apparatus, such as a printer or an electrophotographic copying machine, and more particularly to an image forming apparatus comprising a detachably mountable process cartridge that includes a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner.
2. Description of the Related Art
As has been known, while an image forming apparatus repeats recording operation on recording sheets, toner is used up or a photosensitive drum wears out and deteriorates. When such an inconvenience occurs, it is necessary to replenish toner or replace the photosensitive drum. Also, a cleaning device needs to be replaced when it is filled with waste toner being removed from the surface of the photosensitive drum.
Conventionally, devices such as a photosensitive drum, a cleaning device and so on are normally replaced by a service person. Hence, a user""s urgent demand cannot be met, which has been raising a problem that the service is less satisfactory.
For this reason, a process cartridge accommodating a photosensitive drum and peripheral mechanisms of the photosensitive drum has been employed and becoming increasingly popular in recent years. The process cartridge is detachably mounted to the image forming apparatus main body and can be replaced by a user, thereby facilitating the convenience of maintenance and improving serviceability.
One type of the process cartridge is arranged such that a cleaning device or a developing device is accommodated therein together with a photosensitive drum. Another type of the process cartridge is arranged such that at least one of a charging device, a developing device, or a cleaning device is accommodated therein together with a photosensitive drum.
However, because such a process cartridge puts an emphasis on easy maintenance, a large margin is provided concerning the lifetime of a photosensitive drum, a developing device and a cleaning device accommodated in the process cartridge, in order to ensure a reliable operation of the photosensitive drum and other devices until toner cartridge becomes empty. Thus, in this case, when a process cartridge is replaced at the time a toner cartridge has become empty, a still serviceable photosensitive drum and other devices are also removed, which has been resulting in wastes of these components.
Given such a background, there has been proposed a process cartridge arranged so as to be divided into two portions: a main cartridge accommodating a photosensitive drum and other devices, and a toner cartridge filled with toner. In this case, when the toner is used up, only the toner cartridge is to be replaced, and when deterioration occurs in the photosensitive drum or any other devices after using several toner cartridges, both of the toner cartridge and the main cartridge, that is, a whole process cartridge, is to be replaced.
According to such an arrangement, it is necessary to find the end of the service life of the photosensitive drum, with which several toner cartridges have been used. For example, there is a simple method, by which a main cartridge accommodating a photosensitive drum is to be replaced after replacing toner cartridges for a predetermined number of times.
In this method, however, the predetermined time cannot be selected without an assumption of a standard using condition, such as assuming an average print ratio of a document (ratio of printed area to overall area of a document) as approximately 5% in the case of an A4 size document and a print job of a relatively large number of sheets at a time. On the contrary, actual using conditions cannot be uniform and are diverse. A replacement timing of a toner cartridge or a main cartridge can vary depending on situations, and thus the method is not providing an actual replacement timing of the cartridges.
Examples of cases beyond the standard using condition are such as where a document having a relatively high print ratio is frequently recorded, or oppositely, where a document having a relatively low print ratio is recorded, where a continuous printing or intermittent printing operation is carried out, and so on. Thus, the above simple method cannot be the way to find an actual timing of replacement for a toner cartridge or a main cartridge used under these conditions. For example, in cases where a print operation with a low print ratio is performed most of the time, a film on the photosensitive drum accommodated in the main cartridge wares out to cause a poor image quality before the toner in the toner cartridge is used up.
Hence, there is a need for another method to precisely determine the end of the service life of a photosensitive drum accommodated in a main cartridge. For example, introduction of an optical sensor allows direct judgment of the end of the service life of a photosensitive drum. However, this method cannot be the best under the condition using a toner, because the optical sensor cannot be kept clean.
Instead, there has been proposed another method, by which the service life of a photosensitive drum is detected based on the number of recording sheets having undergone a recording operation or a total time of rotation of the photosensitive drum. For example, Japanese Unexamined Patent Publication JP-A 8-185094 (1996) describes an art of judging the end of the service life of the photosensitive drum based on a total number of rotations of the photosensitive drum.
However, the above method of using a total number of rotations of a photosensitive body, either, is not able to flexibly deal with the change in print ratio resulting in a gap with a standard using condition. Thus, the longer the service period of a photosensitive body, the larger becomes a judging error with respect to the service life of the photosensitive body.
Likewise, in cases where the service life of a photosensitive body is judged based on the number of recording sheets having undergone a recording operation, it is not able to flexibly deal with the change in print ratio resulting in a gap with a standard using condition. Thus, it has been impossible to accurately judge an actual replacement timing of the photosensitive body.
As above, none of the conventional methods is taking into consideration a change of printing condition such that goes out of an assumed standard, thereby resulting in a difficulty in accurately determining an actual replacement timing of a main cartridge accommodating a photosensitive body.
The invention is devised to solve the conventional problems as set forth for example above, and therefore, has an object to provide an image forming apparatus which applies a process cartridge that at least includes a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner, and is capable of precisely judging the service life of the photosensitive body and the replacement timing of the main cartridge.
In order to solve the above problems, the invention provides an image forming apparatus comprising a process cartridge detachably mounted thereto, including a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner; recording sheets counting means for counting a number of recording sheets having undergone a recording operation during a service period of the main cartridge; total operation time measuring means for measuring an operation time of a photosensitive body during the service period of the main cartridge as a total operation time; toner cartridge related operation time measuring means for measuring an operation time of the photosensitive body during a service period of the toner cartridge as a toner cartridge related operation time; toner replenishing time measuring means for measuring a time of replenishing toner from the toner cartridge as a toner replenishing time; and judging means for judging, based on the number of recording sheets counted by the recording sheets counting means, the total operation time measured by the total operation time measuring means, toner cartridge related operation time measured by the toner cartridge related operation time measuring means, and toner replenishing time measured by the toner replenishing time measuring means, at least one of (1) whether the main cartridge needs replacement, (2) whether the toner cartridge needs replacement, and (3) whether a recording operation is allowed or inhibited.
According to the invention, (1) whether the main cartridge needs replacement, (2) whether the toner cartridge needs replacement, and (3) whether a recording operation is allowed or inhibited, are judged based on the number of recording sheets having undergone a recording operation during the service period of the main cartridge, the total operation time of the photosensitive body during which the photosensitive body operates within the service period of the main cartridge, the toner cartridge related operation time of the photosensitive body during which the photosensitive body operates within the service period of the toner cartridge, and the toner replenishing time during which the toner is replenished from the toner cartridge. The toner replenishing time corresponds to a substantial quantity of replenished toner, and therefore, varies in accordance with a print ratio or a using condition, such as continuous or intermittent printing. Thus, it can be said that whether the main cartridge or toner cartridge needs replacement, and whether the recording operation is allowed or inhibited are judged based on the print ratio or a usage pattern, such as the continuous printing or intermittent printing, which makes an accurate judgment possible.
In the invention, it is preferable that the image forming apparatus further comprises invalidating means for invalidating, in cases where the toner cartridge is replaced with another toner cartridge though the toner cartridge is still able to replenish the toner, the toner cartridge related operation time measured by the toner cartridge related operation time measuring means and the toner replenishing time measured by the toner replenishing time measuring means.
According to the invention, when the toner cartridge is replaced inadequately, the toner cartridge related operation time and the toner replenishing time are to be invalidated. Hence, whether the main cartridge or the toner cartridge needs replacement and whether the recording operation is allowed or inhibited can be judged without an error.
Further in the invention, it is preferable that the image forming apparatus comprises displaying means for displaying various kinds of information and toner detecting means for detecting the toner cartridge has become empty, the judging means displays on the displaying means: (1) a message indicating a decrease of the toner when the toner replenishing time measured by the toner replenishing time measuring means has reached a predetermined time; (2) a message indicating that the toner cartridge will soon need replacement, upon judging that the toner cartridge needs replacement, and (3) a message indicating replacement of the toner cartridge when the toner detecting means detects the toner cartridge has become empty.
As above, by displaying up-to-date messages in response to conditions that keep on changing, an urgent job can be avoided, thereby allowing the user to be well-prepared for replacement of toner cartridge.
In the invention, it is also preferable that the toner cartridge related operation time measuring means measures the toner cartridge related operation time of the photosensitive body for a service period in each replacement of toner cartridge, and in replacement of toner cartridge, judging means takes an average of toner cartridge related operation times for all of replaced toner cartridges, and uses the average time as a toner cartridge related operation time.
In the invention, it is also preferable that the judging means initializes the toner cartridge related operation time when the main cartridge is replaced.
In the invention it is preferable that the judging means updates the average time to be used as a toner cartridge related operation time each time the toner cartridge is replaced since the image forming apparatus was activated for a first time.
By the use of an averaged toner cartridge related operation time taken among respective toner cartridges in this manner, it is possible to enhance the accuracy of judging based on the toner cartridge related operation time.
In the invention, it is also preferable that the image forming apparatus further comprises displaying means for displaying various kinds of information and toner detecting means for detecting the toner cartridge has become empty, and the judging means, upon detecting by the toner detecting means the toner cartridge has become empty, inhibits the recording operation and displays on the displaying means a message indicating replacement of the toner cartridge until the toner cartridge is replaced with another toner cartridge, regardless of a reset operation of the image forming apparatus.
In cases where it is detected in this manner that the toner cartridge has become empty, the recording operation is kept inhibited and a message to replace the toner cartridge is kept displayed until the empty toner cartridge is replaced with another toner cartridge regardless of whether or not a reset operation of the image forming apparatus is triggered. Hence, the operation of toner replenishing from an empty toner cartridge does not occur, and thereby idle rotation of a photosensitive body is prevented. Consequently, a waste operation can be eliminated and the service life of the photosensitive body can be extended.
In the invention, it is also preferable that the image forming apparatus further comprises displaying means for displaying various kinds of information and toner detecting means for detecting the toner cartridge has become empty, and the judging means displays on the displaying means: (1) a message indicating a decrease of the toner when the toner replenishing time measured by the toner replenishing time measuring means has reached a predetermined time, and (2) a message indicating that the main cartridge will soon need replacement upon judging that the main cartridge needs replacement, while allowing a recording operation to continue until either the toner detecting means detects that the toner cartridge has become empty or the total operation time measured by the total operation time measuring means reaches a predetermined time.
In the invention, it is also preferable that the image forming apparatus further comprises: displaying means for displaying various kinds of information; and toner detecting means for detecting the toner cartridge has become empty, and the judging means displays on the displaying means: (1) a message indicating a decrease of the toner when the toner replenishing time measured by the toner replenishing time measuring means has reached a predetermined time; and (2) a message indicating that the main cartridge will soon need replacement based on a using condition in accordance with the number of replaced toner cartridges, while allowing a recording operation to continue until the time either the toner detecting means detects the toner cartridge has become empty or the total operation time measured by the total operation time measuring means has reached a predetermined time.
As above, by displaying up-to-date messages in response to conditions that keep on changing, an urgent job can be avoided, thereby allowing the user to be well-prepared for replacement of toner cartridge. In addition, the recording operation is allowed to continue for a while.
In the invention, it is also preferable that the image forming apparatus further comprises displaying means for displaying various kinds of information, and the judging means inhibits a recording operation and displays on the displaying means a message indicating replacement of the main cartridge and the toner cartridge until the main cartridge and the toner cartridge are mounted regardless of a reset operation of the image forming apparatus.
As above, the recording operation is kept inhibited and a message to replace the toner cartridge is kept displayed until the empty toner cartridge is replaced with another toner cartridge without being affected by a reset operation of the image forming apparatus. Hence, an idle rotation of a photosensitive body is prevented. Consequently, a waste operation can be eliminated and the service life of the photosensitive body can be extended.
The invention also provides an image forming apparatus comprising a process cartridge detachably mounted thereto, including a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner; recording sheets counting means for counting a number of recording sheets having undergone a recording operation during a service period of the main cartridge; toner remaining quantity detecting means for detecting a quantity of remaining toner inside the toner cartridge; and judging means for judging whether the main cartridge needs replacement based on the number of recording sheets counted by the recording sheets counting means and a quantity of the remaining toner detected by the toner remaining quantity detecting means.
According to the invention arranged in this manner, whether a main cartridge needs replacement is judged based on the number of recording sheets having undergone a recording operation during the service period of the main cartridge and a quantity of the remaining toner inside the toner cartridge. A quantity of the remaining toner corresponds to a substantial quantity of replenished toner, and therefore, changes in accordance with the print ratio or a using condition, such as continuous or intermittent printing. Thus, it can be said that whether the main cartridge needs replacement is judged based on an actual using condition, which makes an accurate judgment possible.
The invention also provides an image forming apparatus comprising a process cartridge detachably mounted thereto, including a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner; total operation time measuring means for measuring a time during which the photosensitive body operates within a service period of the main cartridge as a total operation time; toner remaining quantity detecting means for detecting a quantity of remaining toner inside the toner cartridge; and judging means for judging whether the main cartridge needs replacement based on the total operation time measured by the total operation time measuring means and a quantity of the remaining toner detected by the toner remaining quantity detecting means.
According to the invention arranged in this manner, whether a main cartridge needs replacement is judged based on the total operation time of a photosensitive body during the service period of the main cartridge accommodating the photosensitive body and a quantity of the remaining toner inside the toner cartridge. A quantity of the remaining toner corresponds to a substantial quantity of replenished toner, and therefore, changes in accordance with the print ratio or a using condition, such as continuous or intermittent printing. Thus, it can be said that whether the main cartridge needs replacement is judged based on an actual using condition.
Further, the invention provides an image forming apparatus comprising a process cartridge detachably mounted thereto, including a main cartridge accommodating a photosensitive body and a toner cartridge for replenishing toner; total operation time measuring means for measuring a time during which the photosensitive body operates within a service period of the main cartridge as a total operation time; toner cartridge related operation time measuring means for measuring a time during which the photosensitive body operates within a service period of the toner cartridge as a toner cartridge related operation time; toner remaining quantity detecting means for detecting a quantity of remaining toner inside the toner cartridge; and judging means for judging whether the main cartridge needs replacement based on the total operation time measured by the total operation time measuring means, the toner cartridge related operation time measured by the toner cartridge related operation time measuring means, and a quantity of the remaining toner detected by the toner remaining quantity detecting means.
According to the invention, whether a main cartridge needs replacement is judged based on the total operation time of a photosensitive body during the service period of the main cartridge accommodating the photosensitive body, the toner cartridge related operation time of the photosensitive body during the service period of the toner cartridge, and a quantity of the remaining toner inside the toner cartridge. A quantity of the remaining toner corresponds to a substantial quantity of replenished toner, and therefore, changes in accordance with the print ratio or a using condition, such as continuous or intermittent printing. Thus, it can be said that whether the main cartridge needs replacement is judged based on an actual using condition.